Becoming Better At Soldering
You have also realized that this standard applies to pipe and fittings. Copper ran into problems with low pH water, as I had previously reported. Brass fittings for PEX also ran into problems.
Quite frankly, NSF 61 is a tough standard. The standard is applicable to any plumbing product that comes in direct contact with potable water. Many plumbing inspectors and health authorities are now enforcing NSF 61. Everything you use, coming in contact with drinking water, must be listed to NSF 61.
One of the products I never thought I would hear much about was flux for copper-soldered joints. The manufacturers didn’t have a difficult time complying with the standard for the flux. Name a major player in the flux business for plumbing systems, and they have a new flux that conforms to NSF 61. Many of the products have new names that indicate the safety aspect of the flux for potable water systems.
However, in parts of the country enforcing NSF 61, I started to receive a rash of phone calls. Large contractors, small contractors, and one-man shops called and asked for the inside scoop of what flux works. For some reason, they thought I knew the ins and outs and had the one brand name up my sleeve of the flux that they should use.
To tell you the truth, I was puzzled. I hadn’t seen any problems with the new NSF 61 fluxes. They worked fine for me. So I started asking what brands the plumbers were using. When they started listing brands that I knew (and liked), I surmised that something was up.
This prompted further inquires with the complaints I was receiving. “What is wrong with the flux? Why do you call the new fluxes junk?” The answer was always the same, “The solder doesn’t flow, you can’t make a decent joint.”
Serious Problem: That is when I realized that we have a serious problem on our hands. The problem, however, is not with the flux, nor with the copper industry, nor with the solder. The problem is us.
We have gotten lazy in the way we make soldered joints. The industry has given us such good products, that it was easy to become lazy. I have never encountered the problems that the plumbers are complaining about because I never forgot how my father trained me to solder.
When you learn from a master, you continue to follow his words of wisdom as a way of paying tribute. That is why I still solder the same way I learned more than 30 years ago. If you have used the new fluxes and have had no problems, like me, you are also probably following the ways of the master who trained you.
If you are having problems with the new fluxes, or are afraid to switch to the new fluxes — read on. (The rest of you, keep up the good work.)
The masters always trained us to use the heat of our torch intelligently. The location of the flame, the direction we aim it, and the gradual rise in temperature were all important points that the masters showed us. We would heat the joints and when they appeared to be up to temperature, we would test the joint with a little solder to see if we had achieved the temperature to flow the solder. When the temperature was achieved, we would flow the solder without applying too much additional heat.
I took pride when I mastered the art of soldering a copper piping system. My father took pride in training all of his sons to solder correctly. (God help you if you ever got caught doing it wrong.)
When we switched from lead-based solders to replacement solders, the temperature required to make a proper solder joint increased by about 100 degrees F. It didn’t take us long to realize that the replacement solders flowed like butter, much better than the lead-based solders. Many solder manufacturers declared that it is virtually impossible to make a bad joint with the replacement solders. This was all before the NSF 61 fluxes entered the market.
So, what is this laziness that we, as an industry, fell into? As one plumber said to me, “We just burn the crap out of the joint and then hit it with a little solder. Bingo, you have a perfect joint. This new solder is great!”
It’s that burning the crap out of the joint that is causing all of the problems. Many plumbers have switched to bigger tips on their torches to get more heat faster to the joint. The burning the crap out of the joint was an effort to reduce the time required to make a soldered joint.
Chemistry 101: Now for a review of chemistry. The component in the flux that makes the solder flow is what chemists refer to as a “salt.” The salt that dominated fluxes in the pre-NSF 61 days was zinc chloride. Zinc chloride is a wonderful component. It is highly forgiving, making it nearly impossible to have a bad joint.
The forgiveness of zinc chloride is that it allows you to raise the temperature of the joint to over 800 degrees F, more than double the heat required to make a proper soldered joint. The zinc chloride is so wonderful that you can raise and lower the temperature numerous times, and the flux would still allow the solder to flow. If you exceeded the high temperature limit, the flux would not flow.
The problem with zinc chloride is that it remains on the inside of the pipe for a long time. It doesn’t wash away when you flush a new system. After a period of time, the zinc chloride can contaminate the drinking water. There is even the possibility of creating a mild form of hydrochloric acid. Hence, it cannot pass NSF 61.
The replacements considered by manufacturers have been alternative salts, such as aluminum chloride and organic. These new salts do not have the temperature limits like zinc chloride. Their high temperature limits are around the 400 degrees F mark. High enough to make a soldered joint, but not high enough to burn the crap out of a joint. If you heat the flux above the high temperature limit, the flux turns black and ugly, and you cannot make the joint. The solder will not flow. You can attempt to brush more flux on the joint, but it still will not flow. Once you exceed the high temperature limit, you have no other choice than to start all over again.
How can you combat this problem of high temperature limit? You have to go back to following the proper procedures for making a soldered joint. The temperature must be raised gradually and the solder tested for flowing capabilities. The days of burning the crap out of a joint are over.